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View Full Version : How does one mic a single flute bit?



shoeshine
07-27-2009, 04:12 PM
OK maybe a stupid question (or just a stupid asker)

But, I have found that for precision tolerence i.e. pressure fittings, I need to mic my bits to get accurate cuts.

So, how does one mic a single flute bit?

Chris

rb99
07-27-2009, 04:42 PM
Good question...Also ho does one mic any bits?

Is there a trick to it?

I also wonder about the accuracy of my lower end digital caliper...

RIB

tmerrill
07-27-2009, 04:59 PM
Chris,

One thought is the actual diameter of the bit is only a part of the equation. Any tolerances in your machine and runout of your router/spindle can affect it.

My suggestion would be to do test cuts in a material that is not affected by grain (such as corian or pvc) or the actual material you will be cutting and measure the width of the cut.

Your results could vary from bit to bit, even from the same manufacturer. So if your dimensions are that critical, I would test every bit you want to use.

Tim

coach
07-27-2009, 05:46 PM
Chris, I would try dial calipers. Place the bit between the jaws and slowly rotate. Record the highest reading. I would do this several times and keep track of the results. That should get it for you. If you don't squeeze I don't think the bit would incur any damage.
Try at different height locations on the bit and see if it is the same.
They have inexpensive plastic calipers at wood supply shops.

Gary Campbell
07-27-2009, 06:03 PM
Chris....
Do a slow test cut into dense material with your single flute bit, and mic the slot.

As far as the "el cheapo" mics go.... I threw away 3 in a few months before I spent the $ and now have used a good one for a couple years.
Gary

gerryv
07-27-2009, 06:28 PM
Not quite as accurate as a good mic. but using the longer jaws of a vernier caliper to measure from the tip "up" the bit rather than across it should give you a pretty good measurement. The resultant measurement compared to the slot measurement Gary suggests should also indicate if there is something else awry. This seems to work for me with my milling machine anyway.

dlcw
08-02-2009, 11:25 PM
I use the method David recommended about rotating the bit between the jaws of the calipers. This has always worked very well for me. As David says, don't squeeze hard on the calipers. Use light pressure and record the largest number when you rotate.

For a material that expands and contracts considerably with climate conditions (wood), a thousandths of an inch is "close enough". Today, in the space of 6 hours that I had a 1" thick by 22" wide glued up plank of Alder on my table held down with vacuum I measured 1/32" decrease in width in the plank. The wood MC was 6% when I started. I think that the drying action of the vacuum comes into play here, but I could be wrong on this. I should have measured MC when I was done but forgot to. I started carving and cutting in the morning when the temperature was about 65 degrees. By the time everything was done the temp was about 85 degrees (thanks in large part to the vacuum motors). Helps me put "tolerances" into perspective.

rhfurniture
08-03-2009, 02:47 AM
Cut a slot and measure that. This gives you the actual cut.
R.